Recovering zinc from its solutions.



ao the-deposits are not readily stripped from v nauaaaa.

T'ElDlERTCK LAIST. AND JAMES ORE, ELTDN, F MACUNDA, MONTANA, ASSTGl-NUHS TU ANECUINDA COPPER MINING COMPANY, Old ANACUNDA, MONTANA; d COEPURMTTUN or non-rune.

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To all whom it may concern:

Be it known that we, FREDERICK lLais'r and f James ORR Enron, citizens of the United States, residing at Anaconda, in the county of Deerlodge and State of Montana, have invented certain new and useful lln'uprovements in Recovering Zinc from lts Solutions, of which the following is a specification. This invention relates td the electrolytic recoveryo'f zinc in regulineformfrom aqueous solutions of its salts.

It is known that the commercial recovery of zinc'by electrodeposition presents serious technical dificulties. The deposit, even when initially satisfactory, tends to become.

poorer in quality as the deposition proceeds,

' the cathodes i r We have found that whenlcertain highlyelectropositive metals, and specifically substantially pure-aluminum, are used as .cathodes for the recovery of zinc fromits solutions ,.'the operation proceeds with relative smoothness and regularity, and with com- 'pa-ratively good current efficiencies; such cathodes will moreover take an excellent deposit of zinc for an indefinite period; that is to say, the cathode may be repeatedly used, the deposited metal bcingstripped at appropriate intervals in accordance with the.

usual metallurgical practice.

,We have observed however that the pres.-' ence of certain metallic or other; impurities in or on the aluminum surface exerts a pro-- found influence uponthe course of the deposition. For example, an aluminum plate containing four or five per cent. of copper will often take no deposit of zinc, no matter how long it may be left inthe electrolyte, orhow strong a current may be used. The zinc appears to'dissolve practically as rapidly as it is deposited. Similarly,'an aluminum cathode containing only one or two per cent. of copper will scarcely take a do .posit of zinc after it has been used a few times; whereas a substantially pure aluminum plate, for example a plate containing no copper or only a small fraction pf a per cent. of this metal, will under precisely-the same electrolytic'conditions take an entirely satisfactory deposit for an indefinite period.

This sheet is especially marlred in the dpecidcatlon of Letters Patent;

.llppli cation filed 1 unc 1c, 1916. aerial No. ioaosr.

Patented Tell... 5, till eleetrodeposition of zinc from acid solutions for examp e to'inetallic impurities in the electrolyte; and according to our observations asaloove noted it appliesequally to the presence of electronegative impurities in or on the aluminum cathode. llt is likely that copper, for example, forms a couple-with the electrodeposited zinc, thereby greatly increasing its rate of solution. Pure alumi num onthe other hand, on account of its highly electropositive.character, is found to, be quite free from any tendency to promote the-solution of zinc. .f

The above-described eflect ofpure aluminum cathodes is as might be expected de pendent upon the surface conditionsf -rl or example, such alloys as aluminum bronze areincapable of receiving a good deposit ofzinc. If, however, a sheet of such alloy be.

treated with nitric acid to dissolve the impurities or allo'ying metal, the resulting film of alumina being then removed, the plate will take an excellent deposit for affew days, or until the-pure aluminum surface has become contamlnated'or has worn 0E, expos- ,ing a surface of impure aluminum, and rendering necessary another acid treatment.

Inasmuch as, the favorable effect of aluminum upon the deposition is-presumably due to its highly" electroposi'tive character, it is to be expected that other metals more electropositive than zinc, for instance magnesium, 'will give similar results. The essential condition for eifective work appears to be that the cathode should bemore electropjositivethan zinc, and should be either quite free as regardsits exposed surface from relatively electronegative impurities,

or so nearly free therefrom that their influence upon the solution of the deposited zinc 'becomes negligible.

We claim:- l r l.'The process of recovering zinc from its solutions, which consists in passing an electric current through a solution containing a nine salt to a cathode presenting a surface of a metal more electropositive than Zinc-, said surface being substantially free from impurities electronegative to zinc, until a deposit suitable for stripping has been formed.-

- 2. The process of recovering zinc from its solutionsfwhich consists in'passing an electrio current through a solution'containing a 'zinc salt toja'cathode presenting a surface 10 of aluminum substantially free from impurities electronegative to zinc, until a-deposit suitable for stripping has been formed.

3. The process of recovering zinc from its solutlons, whlch consists in 'passlng an electric current through a solution containing a I zinc salt to a cathode presenting a surface FREDERICK LAIST.

JAMES ORR, ELTON.- 

